Biomedical subjects

X Y He

Publications and source records attributed to X Y He.

At least 55 records · Page 3Linked to original sources

PubMed1994

Direct comparison of the relationship between clinical outcome and change in CD4+ lymphocytes in human immunodeficiency virus-positive homosexual men and injecting drug users.

BACKGROUND AND METHODS: To compare rates of decline of CD4+ lymphocytes among human immunodeficiency virus-positive homosexual men and injecting drug users, we followed up prevalent human immunodeficiency virus-positive homosexual men and current or former injecting drug users from February 1988 through August 1991. Subjects were free of acquired immunodeficiency syndrome at study entry and had semiannual clinical and laboratory evaluation, including measurement of T-cell subsets, under common protocols. Initial levels and rates of change of CD4+ lymphocyte counts were compared according to cohort membership and clinical progression, defined by the development of thrush or an acquired immunodeficiency syndrome--defining illness. Median follow-up was 30 months for both cohorts. RESULTS: At study entry, homosexual men had lower absolute numbers of circulating CD4+ lymphocytes than did injecting drug users (459/microL [0.46 x 10(9)/L] vs 509/microL, respectively). During follow-up, homosexual men exhibited a faster decline in CD4+ lymphocyte counts as well as more frequent development of HIV-related symptoms (thrush or acquired immunodeficiency syndrome). In both cohorts, initial levels of CD4+ lymphocytes and rates of decline in these cells were strongly associated with progression of disease, defined as remaining asymptomatic, onset of thrush, or onset of acquired immunodeficiency syndrome. Once homosexual men and injecting drug users were stratified by disease progression, their initial levels and rates of decline of CD4+ lymphocyte counts were similar. Thus, crude differences between the two study groups largely resulted from differences in development of clinical symptoms. CONCLUSIONS: In these cohorts of homosexual men and injecting drug users, clinical outcome was much more important than risk group membership in determining changes in CD4+ lymphocyte numbers. The close similarity between the groups also suggests that drug use, ethnicity, and socioeconomic status play a minor role in the progression of human immunodeficiency virus infection.

Adult↗

PubMed1994

Transcriptional regulation and chromatin structure of the human CD34 gene promoter region.

The human CD34 surface antigen is selectively expressed on stem/progenitor cells within the hematopoietic system. Because CD34 expression is tightly linked to the immature status of hematopoietic cells, with expression being rapidly lost as hematopoietic cells mature and differentiate, an examination of its regulation may provide important insights into the molecular control of blood cell development. A comparison of the CD34 nuclear transcription rate in CD34+ and CD34- cells indicated that the CD34 gene is transcriptionally regulated in hematopoietic cell lines. In a previous report, we had identified two major clusters of CD34 transcription initiation sites by 5' RACE (rapid amplification of cDNA ends) analysis. In transient transfection experiments, we now demonstrate the ability of sequences encompassing each of these clusters to function as promoters of transcription in CD34+ cells. These promoters functioned at equivalent levels in CD34+ and CD34- cells, and the addition of 5' flanking sequences, extending as far as 3.7 kb upstream, to the core promoters did not differentially modify the level of expression in CD34+ versus the CD34- cell lines. An examination of DNase I hypersensitivity sites within an 18-kb segment of DNA, extending 9 kb either side of the proximal promoter, showed six sites that were primarily associated with CD34- expressing cells. Taken together, these data indicate that the CD34 promoter sequences alone do not confer tissue-or stage-specific expression. Appropriate transcriptional regulation of the CD34 gene must be controlled by chromatin structure, as identified by DNase I hypersensitivity, and/or by other tissue- and stage-specific elements present outside of the promoter region.

Antigens, CD↗

PubMed1994

Primary structure of the large subunit of trifunctional beta-oxidation complex from pig heart mitochondria.

The amino-terminal and internal sequences of the isolated large subunit of trifunctional beta-oxidation complex from pig heart mitochondria were determined by Edman degradation. The results demonstrated that the sequence of this novel beta-oxidation enzyme is identical with the sequence recently reported for a porcine gastrin binding protein that serves as the gastrin receptor on parietal cell surfaces. Evidence is provided to show that it is unlikely that the porcine gastrin binding protein has such a sequence. The data lead us to conclude that the mature large subunit of porcine trifunctional beta-oxidation complex is composed of 727 amino acid residues with a calculated molecular weight of 79,113, while the precursor of this long-chain fatty acid oxidation enzyme has a mitochondrial presequence consisting of 36 residues and a calculated M(r) of 83,099.

Amino Acid Sequence↗

PubMed1994

Characterization of putative small nuclear RNAs from Giardia lamblia.

Small nuclear RNAs (snRNAs), which have roles in RNA metabolism, have been found in all eukaryotic cells. Candidate snRNAs were identified in the primitive protozoan parasite, Giardia lamblia, by either immunoprecipitation of total RNA with antiserum directed against the 2,2,7-trimethylguanosine cap structure characteristic of snRNAs or by Northern hybridization with oligonucleotide probes complementary to snRNA consensus sequences. Isolated putative snRNAs include eight 2,2,7-trimethylguanosine-capped species: RNAs A through H, and one non-2,2,7-trimethylguanosine-capped species: RNA J. Single copy genes encoding RNA D, RNA H and RNA J were cloned and sequenced, and the 5' end of each RNA was determined by primer extension analysis. Certain characteristics suggest tentative identification of these Giardia RNAs as nucleolar RNAs with possible roles in rRNA processing.

Animals↗

PubMed1994

Short-term diethylnitrosamine-induced oval cell responses in three strains of mice.

The oval cells of the liver have been identified as target cells of chemical carcinogens during rat hepatocarcinogenesis and are believed to act as liver stem cells. In this study mice (strains C3H/EJ (C3H), C57/BL6J (C57) and hybrid B6C3F1 (F1)) were sacrificed at 1, 3 and 7 days after administration of a single dose of the carcinogen diethylnitrosamine (DEN), and histopathological studies of oval cells were evaluated using Haematoxylin and Eosin (H&E), Picro-Mallory (P-M), alpha-fetoprotein (A-FP) and glutathione S-transferase placental form (GST-pi) staining techniques and electron microscopy (EM). Increased oval cell proliferation was observed as soon as one day following exposure of the mice to DEN, in a manner consistent with C3H and C57 mice exhibiting high and low susceptibility to DEN respectively, with hybrid F1 mice being intermediate in DEN sensitivity. This analysis indicates that, in mice, oval cells are target cells at very early stages of liver carcinogenesis and supports the notion that oval cells are potential liver stem cells.

Animals↗

PubMed1994

Photodynamic therapy with photofrin II induces programmed cell death in carcinoma cell lines.

The mode of cell death following photodynamic therapy was investigated from the perspective of programmed cell death or apoptosis. Human prostate carcinoma cells (PC3), human non-small cell lung carcinoma (H322a) and rat mammary carcinoma (MTF7) were treated by photodynamic therapy. An examination of extracted cellular DNA by gel electrophoresis showed the characteristic DNA ladder indicative of internucleosomal cleavage of DNA during apoptosis. The magnitude of the response and the photodynamic therapy dosage required to induce DNA fragmentation were different in PC3 and MTF7. The MTF7 cells responded with rapid apoptosis at the dose of light and drug that yielded 50% cell death (LD50). In contrast, PC3 showed only marginal response at the LD50 but had a marked response at the LD85. Thus, apoptosis did not ensue as quickly in PC3 as in MTF7. The H322a cells were killed by photodynamic therapy but failed to exhibit any apoptotic response. The results also suggested that apoptosis in these cell lines has a minor requirement for de novo protein synthesis and no requirement for de novo RNA synthesis. This study indicates that although apoptosis can occur during photodynamic therapy-induced cell death, this response is not universal for all cancer cell lines.

Animals↗

PubMed1994

[Determination of hexamethylene bisacetamide in plasma by high performance liquid chromatography].

A high performance liquid chromatographic assay was developed for determination of the plasma concentration of hexamethylene bisacetamide (HMBA) in rabbit. Plasma samples were vortex-mixed with 0.3 ml of methanol and centrifuged at 10000 r/min for 5 min. A 20 microliters aliquot of the supernatant was injected into the HPLC system. Analysis was performed on a Du Pont Zorbax C18 column (250 mm x 4.6 mm, 10 microns) with a precolumn (50 mm x 4.6 mm, 10 microns, YWG-C18). The eluent was methanol--water (30:70), with flow rate of 1.0 ml.min-1 and UV detection at 210 nm. The limit of detection was 1.0 microgram.ml-1 in plasma and the calibration curve was linear over the range 5-1000 micrograms.ml-1 (r = 0.9988). The HPLC assay was applied for studying the pharmacokinetics of HMBA in rabbit.

Acetamides↗

PubMed1993

Modulation of human T cell responses by nitric oxide and its derivative, S-nitrosoglutathione.

OBJECTIVE: To examine the effects of nitric oxide (NO) and its more stable derivative, S-nitrosoglutathione (SNO-GSH), on the response of activated T lymphocytes. METHODS: The effects of NO and SNO-GSH on DNA synthesis, interleukin-2 (IL-2) production, IL-2 receptor expression, and cGMP accumulation were determined in phytohemagglutinin-activated peripheral blood mononuclear cells (PBMC) and spleen T cells. RESULTS: Nitric oxide (half-life [T1/2] < 15 seconds) did not inhibit T cell proliferation. However, the derivative SNO-GSH (25 microM) (T1/2 > 2 hours) inhibited DNA synthesis by a mean +/- SD of 65 +/- 19.6% (P < 0.001) in PBMC and 75 +/- 15% (P < 0.001) in spleen cells. Macrophage depletion of PBMC did not abrogate the inhibition. SNO-GSH had no effect on IL-2 production or IL-2 receptor expression. NO (25 microM) increased the cGMP content of PBMC (0.65 +/- 0.15 pmoles/10(6) cells; P < 0.04), as did SNO-GSH (25 microM) in both PBMC (3.8 +/- 1; P < 0.001) and spleen T cells (5.2 +/- 1.2; P < 0.001). Methylene blue and hemoglobin, which are NO inhibitors, inhibited SNO-GSH-induced cGMP accumulation (P < 0.001). CONCLUSION: SNO-GSH inhibits T cell DNA synthesis independently of IL-2 production and in association with cGMP accumulation via a NO-dependent mechanism. We suggest that NO and its S-nitrosothiol derivatives may act as endogenous inhibitors of T cell-mediated inflammation.

Cyclic GMP↗

PubMed1993

Purification and characterization of the trifunctional beta-oxidation complex from pig heart mitochondria.

The presence of a trifunctional beta-oxidation complex in pig heart and its relationship to the known long-chain enoyl-CoA hydratase (EC 4.2.1.74) from pig heart mitochondria were investigated. For this study, the complex was partially purified by chromatography on DEAE-cellulose in the absence of detergents and was purified to near homogeneity in the presence of Triton X-100. Both enzyme preparations contained long-chain specific activities of enoyl-CoA hydratase, L-3-hydroxyacyl-CoA dehydrogenase, and 3-ketoacyl-CoA thiolase but were virtually inactive toward short-chain (C4) substrates. Both preparations exhibited very low or no activities of delta 3,delta 2-enoyl-CoA isomerase (EC 5.3.3.8) and 2,4-dienoyl-CoA reductase (EC 1.3.1.34). The molecular weights of the two subunits of the pig heart complex were estimated to be 81,000 and 45,000, respectively. The partially purified preparation, obtained in the absence of detergent, was identified as a membranous fraction enriched with respect to the inner mitochondrial membrane. It is concluded that long-chain enoyl-CoA hydratase is a component enzyme of the trifunctional beta-oxidation complex which is associated with the inner membrane of pig heart mitochondria.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1992

Inhibition of enoyl-CoA hydratase by long-chain L-3-hydroxyacyl-CoA and its possible effect on fatty acid oxidation.

The kinetics of bovine liver enoyl-CoA hydratase (EC 4.2.1.17) or crotonase with 2-trans-hexadecenoyl-CoA as a substrate were studied because different rates were obtained with two assay methods based on measurements of substrate utilization and product formation, respectively. L-3-Hydroxyhexadecanoyl-CoA, the product of the crotonase-catalyzed hydration of 2-trans-hexadecenoyl-CoA, was found to be a strong competitive inhibitor of the enzyme with a Ki of 0.35 microM. In contrast the short-chain product, L-3-hydroxybutyryl-CoA, is a weak competitive inhibitor with a Ki of 37 microM. L-3-Hydroxyhexadecanoyl-CoA is a much stronger inhibitor of crotonase than are other short-chain and long-chain intermediates of beta-oxidation and crotonase is more severely inhibited by this compound than are all beta-oxidation enzymes tested so far. Determination of true kinetic parameters for the crotonase-catalyzed hydration of long-chain substrates requires the removal of product in a coupled assay. When this was done, the Km for 2-trans-hexadecenoyl-CoA with bovine liver crotonase was found to be only 9 microM. It is suggested that under conditions of restricted beta-oxidation, when 3-hydroxyacyl-CoAs accumulate in mitochondria, the inhibition of crotonase by long-chain 3-hydroxyacyl-CoAs may limit the further degradation of medium-chain and short-chain intermediates of beta-oxidation.

Acyl Coenzyme A↗

PubMed1992

Isolation and molecular characterization of the human CD34 gene.

The human CD34 surface antigen is selectively expressed on hematopoietic stem/progenitor cells, suggesting that it plays an essential role in early hematopoiesis. Using a 1.5-kb partial human CD34 cDNA sequence, RNA-polymerase chain reaction (PCR), and rapid amplification of cDNA ends (RACE) methods, we cloned and sequenced the full-length (2.65 kb) cDNA. The cDNA encodes a type I transmembrane protein with no obvious homology to other known proteins. The entire CD34 gene of 28 kb was cloned, and the coding sequences mapped to eight exons. Mapping of the 5' termini of mRNAs by 5'-RACE and RNAase protection analyses has indicated that the human CD34 gene uses multiple transcription initiation sites. Analysis of the upstream regulatory sequences revealed the absence of TATA and CAAT box sequences, and the presence of myb, myc, and ets-like DNA binding motifs. We have identified significant homology between human and mouse CD34 genes in 5' and 3' untranslated regions, amino acid coding sequences, and 5' flanking sequences. This investigation of the CD34 gene should facilitate study of the function and regulation of this stem cell antigen.

Amino Acid Sequence↗

PubMed1992

[Characteristics of traditional Chinese medicine syndromes in both spontaneous and variant angina. An analysis of 21 cases].

An analysis of TCM syndromes is reported in 21 cases with both spontaneous and variant angina as compared with 147 cases with effort angina. The results showed that 3 characteristic features were present, which were as follows: the Biao-Shi syndrome of cold condensation was more than that of the control group in ratio of 42.86% to 3.40%; the Ben-Xu syndrome of Yang deficiency was more and that of Qi deficiency less than those in the control group, and they were in ratio of 33.33% to 6.12% and 33.33% to 72.11% respectively. An absolute reduction of blood supply resulted from coronary spontaneous spasm in both spontaneous and variant angina causes severe chest pain during attacks as a cold condensation type. Hyperfunction of parasympathetic nerves often occurring in coronary heart disease with Yang deficiency is liable to vasoconstriction of the large coronary arteries leading to episodes of both spontaneous and variant angina. The presence of less Qi deficiency type may be related to the less impairment of cardiac function resulted from the short course in these cases and only relatively mild state of an illness, even no marked lesion in coronary arteries in a part of patients with both spontaneous and variant angina. No significant difference in TCM syndromes occurred between spontaneous and variant angina. Both Yang and Yin deficiency, as the Ben-Xu syndromes, were more present in angina of cold condensation type.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

[Improved technics in 578 abdominal total hysterectomies].

This paper reports the improved technics in 578 abdominal total hysterectomies. After dividing the infundibulo-pelvic ligaments and both layers of the broad ligaments the ovarian vessels were dissected out, cut and ligated, the utero-sacral ligaments revered but not ligated, and if necessary, the bleeding points were tied. After cutting the intervening tissues on both sides of the uterus, the uterine vessels could be identified, clamped and ligated at level below the cervical internal os. The cut edges of the vaginal cuff had to be approximated exactly, avoiding too close and too tight sutures. There was no organ injured during the operations, no abdominal pain nor hemorrhage from the cut edge of vaginal cuff after operation. Of the 520 patients followed up after operation, 518 cases had good healing at the vaginal stumps with granulation in only 2 cases, the effect with this improved method of hysterectomy has been considered satisfactory.

Arteries↗

PubMed1990

Markers of multiple hematopoietic-cell lineages in multiple myeloma.

Multiple myeloma is considered a cancer of mature plasma cells. Recent studies, however, suggest the possible involvement of early B cells and the expression of myelomonocytic antigens by myeloma cells. Using flow cytometry, we searched for evidence of the expression of genes specific for different hematopoietic lineages by tumor cells in bone marrow aspirates from 27 patients with aneuploid multiple myeloma. In addition to features characteristic of myeloma cells, we found evidence of the frequent expression by myeloma tumor cells of the pre-B-cell antigen CALLA (common acute lymphocytic leukemia antigen) (in specimens from 58 percent of patients) and of megakaryocytic (88 percent), myelomonocytic (65 percent), and erythroid (39 percent) surface markers. The proportion of tumor cells expressing the different markers varied among patients, from 2 to 100 percent of recognizable tumor cells. We conclude that cells of multiple lineages are involved in myeloma--a finding that is consistent with the hypothesis that there is a common primary neoplastic lesion for all hematologic cancers.

Aneuploidy↗

PubMed1990

[A study on the decomposition kinetics of vitamin C powder].

The effect of temperature and humidity on the discoloration and degradation of vitamin C powder was studied via accelerated test under isothermal and constant humidity conditions. The changes of color and concentration of vitamin C were monitored by diffuse reflectance spectroscopy and iodimetry respectively. Under the condition of relative humidity less than the critical relative humidity, the apparent rate constant of discoloration of Kc of vitamin C powder is: kc = 'exp (-Ea/RT) exp (m 'RH), where k' and m' are constants, RH is relative humidity and Ea is activation energy, when RH less than 70%, Ea = 104.33 kJ . mol-1. The degradation curve of vitamin C powder under various temperatures and humidities can be expressed by C = N/(1 + Btn), the rate equation of degradation of vitamin C powder is: -dC/dt = kdC(1 + 1/n) (N-C)(1 - 1/n), where kd is the apparent rate constant of degradation, B and n are constants, N is the initial content of vitamin C and C is the content of vitamin C at time t. When RH are 97, 93, and 79.5%, Ea are 86.87, 88.22 and 202.64 kJ.mol-1, respectively.

Ascorbic Acid↗

PubMed1990

The double porosity model for mass transfer between capillaries and tissues in lung microcirculation.

This paper proposes a double porosity model to deal with the mass transfer between capillaries and tissues in the lung microcirculation on the basis of. Utilizing the analytic method of small parameter expansion and the numerical method, the nonlinear governing equations are solved. Comparison shows that the small parameter solution is accurate enough to illustrate the mass exchange between the lung capillary and tissues. Finally the results are used to discuss the mechanism of formation of lung edema.

Capillaries↗

PubMed1989

Assay of L-3-hydroxyacyl-coenzyme A dehydrogenase with substrates of different chain lengths.

A method for assaying L-3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35) which permits rate measurements with L-3-hydroxyacyl-CoA substrates of various chain lengths at physiological pH is described. The method is based on a coupled assay system in which 3-ketoacyl-CoA compounds formed by the dehydrogenase are cleaved by 3-ketoacyl-CoA thiolase (EC 2.3.1.16) in the presence of CoASH. The advantages of this assay method are its irreversibility and elimination of product inhibition. The assay procedure was used to determine the kinetic parameters (Km, Vmax) of pig heart L-3-hydroxyacyl-CoA dehydrogenase with several substrates of various chain lengths. The data obtained show the enzyme to be most active with medium-chain substrates whereas Km values for medium-chain and long-chain substrates are almost equal but much lower than those previously reported.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1989

[Simultaneous determination of carbamazepine and its active metabolite in serum by high performance liquid chromatography].

A rapid, sensitive and simple to operate high performance liquid chromatographic method for the simultaneous determination of carbamazepine (CBZ) and its metabolite (10,11-epoxide carbamazepine, ECBZ) in serum has been developed. The sample was extracted with ethyl acetate. The extract was evaporated to dryness and taken up with the mobile phase. Separation of CBZ and ECBZ was achieved by reversed phase chromatography using a mobile phase consisting of methanol-water (1:1) at flow rate of 0.8 ml/min on a 5 microns YWG C-18 column. Eluent was monitored at 214 nm. The method has a good linearity. The recoveries of CBZ and ECBZ were found to be 99.7% +/- 2.45 and 97.3% +/- 4.20 respectively. Precision studies for both within day and day-to-day at different concentrations provided CV values of less than 6%. Some commonly used anticonvulsants can be determined in the same procedure without interference. This method well adapted to the therapeutic monitoring of CBZ treated patients, as well as for pharmacokinetic studies.

Carbamazepine↗